His foot is probably resting on a bull, which is consistent with his Taurus nature. I don’t think it’s a living creature; it seems to be a stone or carved representation of one.
He’s wearing armor under his robes. This might indicate that he’s always prepared for battle should it be necessary. It might also hint that he’s rigid; that his word is Law and must be obeyed. By the same token, he doesn’t threaten to use his power – he keeps it under his robes, ready but not intimidating.
He is outside of his castle, showing that he participates in worldly matters – doesn’t hide in his fortress.
As with all the Kings, he wears what is called a “cap of maintenance” under his crown. I encountered this idea from, I think, Waite. I don’t yet understand the significance of this; haven’t had time to research it, but it’s something to think about.